Methods and apparatus for cooling high-temperature-superconducting, microelectronic components must meet very high demands regarding the constancy of the cooling temperature as well as the avoidance of negative influences on the microelectronic components due to electromagnetic and mechanical oscillations or vibrations of the cooling apparatus. Especially because such microelectronic components have a very small tolerance for or resistance to vibrations, no practical cooling systems exist in which compressor equipment is used for providing the cooling.
Prior apparatus rely on complicated, costly and only partially successful mechanical measures for damping out or isolating from the electronic component the vibrations produced by a cooling machine, such as a Stirling machine. Such arrangements are disclosed in German Patent 3,445,674 and German Patent Laying-Open Document 3,639,881. According to these two German Patent Publications, an electronic component is thermally coupled to the cooling station of a cooling machine, such as a Stirling machine, by a flexible, thermally conducting metal band or strap. In this manner, heat can be removed from the electronic component while it is at least partially isolated from the mechanical vibrations of the cooling machine.
In order to completely avoid the mechanical vibrations of a cooling machine, it is also known to cool an electronic component using a cryogenic liquid that is delivered to the cooling location in a controlled manner from a storage container, such as a Dewar flask. German Patent Laying-Open Document 4,033,383 discloses such a cooling system for electronic components. In the disclosed system, a vaporization chamber is arranged in communication with the cryogenic liquid storage container. The electronic component is mounted on a thermally conducting cooling finger, which extends into the vaporization chamber. The heat conducted away from the component causes the cryogenic fluid in the vaporization chamber to evaporate, whereby the finger and the component can be cooled down to the vaporization temperature. The temperature can be controlled by controlling an electric heater near the cooling finger and also by adjusting a throttle valve through which the evaporated cooling medium returns from the vaporization chamber to the storage container. In the disclosed embodiments, nitrogen is used as the cryogenic fluid.
Even though no compressor or other cooling machine is involved in the above described cooling system, vibrations still arise and negatively influence the operation of the electronic component due to the boiling of the cryogenic liquid. Namely, as the cryogenic cooling medium evaporates, bubbles of the medium boil up in the vaporization chamber and cause vibrations of the cooling finger, which directly conducts the vibrations to the electronic component. Furthermore, the system is not a closed or sealed system, and it is necessary to refill additional cryogenic liquid into the storage container after a certain period of cooling operation.
Another known cooling system for electronic sensors includes a condenser for nitrogen arranged on the cold head or cold end of a Stirling machine. An evaporator is arranged to cool the sensor elements and is connected to the condenser by respective conduits for the liquid and gaseous nitrogen. The use of conduits, which have a capillary size, substantially decouples the vibrations of the Stirling machine from the evaporator and the sensor elements. However, for certain applications such an arrangement is too costly and complicated. Furthermore, such an arrangement cannot ensure a total isolation or freedom from vibration at the measuring point of the electronic sensors.